1. Field of the Invention
The present invention relates to rotary switches which may be used in electronic equipment or the like.
2. Description of the Related Art
An example of a conventional rotary switch is shown in FIG. 10. This rotary switch includes a case 1, a rotary switch knob 2, a rotor 3, and a contact spring 9. The rotary switch knob 2 is rotatably mounted on the case 1 by an E-shaped retaining ring 5. The rotor 3 is directly linked to the rotary switch knob 2 by attaching the rotor 3 to the knob 2. The contact spring 9 is attached to rotor 3 by, for example, heat caulking or an equivalent method. When the rotary switch knob 2 is rotated through an angle, the rotor 3 together with the contact spring 9 rotate through an equal angle.
Thus, with the conventional rotary switch, the rotary switch knob 2 and the rotor 3 are directly linked with each other because they are fitted together, or fixedly attached to each other by an equivalent method. Accordingly, the angle of rotation of the rotary switch knob 2 and the rotor 3 and integral contact spring 9 are always the same. This is, however, disadvantageous for a number of reasons.
When two or more circuits have to be formed along a common circumference, the rotary switch knob 2 must be restricted from rotating beyond 180.degree. (the maximum range of a single circuit in a circumference containing two equal sized circuits) because 180.degree. is the maximum range of a single circuit in a switch using two or more circuits. This limits the freedom of design of the switch.
Conversely, when the angle range within which the rotary switch knob 2 can be rotated (per circuit) is set at a certain angular quantity, then this set quantity determines the number of circuits which can be formed along a common circumference. (For example, if the angle range of knob 2 is 120.degree., then three circuits can be formed along a common circumference.) As a result, when the rotational angle range of knob 2 is great, and the number of circuits along the circumference is also great, it may be necessary to increase the number of circuit blocks. This results in the rotary switch structure being complicated, and having a great size.
On the other hand, when a large number of contacts have to be provided per circuit, it is necessary to reduce the pitch (the angle between adjacent contacts) at which a pattern is formed on a printed circuit board. This means that the pitch (the angle between adjacent positions) at which the rotary switch knob 2 rotates for switching must be accordingly reduced.